JP3754316B2 - Coating film forming method and coating film forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for forming a coating film by applying, for example, a coating liquid for a protective film of a device to a substrate to be processed such as a semiconductor wafer or an LCD substrate (glass substrate for liquid crystal display).
[0002]
[Prior art]
As one of semiconductor manufacturing processes, there is a process of applying polyimide on a substrate such as a semiconductor wafer in order to form a protective film or an interlayer insulating film of a semiconductor device. As one method of this coating treatment, a chemical solution in which polyimide is dissolved in a solvent is further diluted with a solvent before coating. For example, the wafer W is rotated as shown in FIG. The coating liquid is discharged onto the surface of the wafer W while being gradually moved in the substantially horizontal direction in the radial direction, and the coating liquid is spirally applied in the manner of a single stroke, and then the wafer is heated to volatilize the solvent, Next, a cooling method has been studied.
[0003]
In this method, when the discharge amount of the coating liquid from the coating liquid nozzle 11 is constant, the moving speed of the nozzle 11 is gradually changed so as to be faster in the central area of the wafer W and slower in the peripheral area. Adjustment is made so that the film thickness of the coating solution is uniform in the plane.
[0004]
[Problems to be solved by the invention]
However, even if the coating liquid is applied by changing the moving speed of the coating liquid nozzle 11 by the above-described method, the coating liquid 12 is applied to a thickness of about 10 μm, for example, on an 8-inch wafer W and heated. Then, when dried, as shown in FIG. 12, it is recognized that the outermost film thickness rises by about 0.5 μm from the film thickness of other regions. When the outermost film thickness is increased in this manner, development characteristics and etching characteristics in subsequent processes are changed, and there is a possibility that a hole is not opened or a part that is not etched is generated.
[0005]
The reason is considered as follows. In the peripheral area of the wafer W, since it volatilizes also from the side edge, the amount of volatilization in the peripheral area is larger than that in other areas, thereby increasing the volatilization rate of the solvent in the peripheral area. Thus, if the volatilization rate of the solvent is different, the temperature is lowered due to volatilization and the surface tension is increased due to volatilization at the site where the volatilization rate is large, and the liquid is attracted to the outside. The film thickness becomes large. Thus, in this example, since the volatilization rate of the solvent is large in the peripheral region as shown in FIG. 12, the solidification of the polyimide in this part is accelerated, and it is assumed that the film thickness is increased as a result.
[0006]
The present invention has been made based on such circumstances, and its purpose is to provide a technology capable of ensuring high uniformity in film thickness when, for example, a coating film mainly composed of polyimide is formed on a substrate. It is to provide.
[0007]
[Means for Solving the Problems]
In the coating film forming method of the present invention, the component of the coating film and the solvent are applied from the coating nozzle provided facing the surface of the substrate while rotating the substrate holding portion that holds the substrate substantially horizontally about the vertical axis. In the coating film forming method of moving the coating nozzle from the center of the substrate toward the peripheral side while discharging the coating solution containing the coating liquid , thereby spirally coating the coating solution on the surface of the substrate ,
A step of applying the first region of the coating film forming region by moving the coating nozzle from the center of the substrate toward the first position while discharging the coating liquid to the first position ;
Next, the coating nozzle is moved toward the peripheral side of the substrate while discharging the coating liquid, and is applied to the second region which is the peripheral region of the substrate outside the first region. Spraying the solvent of the coating film onto the second region from a spray nozzle that moves toward the peripheral side .
[0008]
Such a method includes a substrate holding part for holding the substrate substantially horizontally;
A rotation mechanism for rotating the substrate holding portion around a substantially vertical axis;
Provided surface facing the substrate, and the coating nozzle for discharging a coating solution containing a component and a solvent for the coating film to the substrate surface,
A spray nozzle for spraying the solvent of the coating film on the peripheral region of the coating film forming region of the substrate;
The coating film forming apparatus includes a moving mechanism that moves the coating nozzle and the spray nozzle in a substantially horizontal direction in the radial direction of the substrate .
[0009]
According to such an invention, the amount of the solvent is applied to the peripheral region of the substrate where the amount of heat radiation is large and the solvent of the coating film is liable to volatilize than the other regions. The degree of volatilization of the solvent can be aligned. As a result, the solidification rate of the coating film, which depends on the degree of solvent volatilization, is almost the same throughout the substrate surface, so that the coating film thickness is uniform throughout the substrate surface, ensuring high uniformity of the film thickness. can do.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
A coating film forming apparatus for carrying out the coating film forming method according to the present invention will be described below. First, the overall configuration of this apparatus will be briefly described with reference to FIGS. In the figure, reference numeral 21 denotes a cassette station, for example, a delivery for transferring the wafer W between the cassette placement part 22 for placing a cassette C containing 25 wafers W and the placed cassette C. An arm 23 is provided. A processing unit S <b> 1 surrounded by a casing 24 is connected to the back side of the delivery arm 23. A main conveying means 25 is provided at the center of the processing unit S1, and a plurality of coating units 31 are provided on the right side, for example, so as to surround the main conveying means 25, and a heating / cooling system is provided on the left side, front side, and back side. Shelf units U1, U2, and U3 are stacked in multiple stages.
[0011]
The shelf units U1, U2, and U3 are configured by combining various units for performing pre-processing and post-processing of the coating unit 31, and the combination is, for example, in the coating unit 31 as shown in FIG. The wafer W having the coating solution coated on the surface is dried in a reduced pressure atmosphere, the reduced pressure drying unit 32 that volatilizes the solvent contained in the coating solution, the heating unit 33 that heats (bakes) the wafer W, and the wafer W is cooled. The cooling unit 34 is included. For the shelf units U2 and U3, a delivery unit 35 having a delivery table for delivering the wafer W is also incorporated. Further, the main transfer means 25 described above is configured to be movable up and down and back and forth and to rotate around a vertical axis, for example, and the wafer W between the units constituting the coating unit 31 and the shelf units U1, U2, and U3. It is possible to deliver.
[0012]
Next, the coating unit 31 will be described with reference to FIGS. Here, the casing that forms the exterior body of the coating unit 31 is omitted. In this casing (not shown), for example, a hollow case in which an opening (not shown) for loading and unloading the wafer W is formed on the side. A body 41 is provided, and a wafer holder 42 that forms a substrate holder that vacuum-sucks the wafer W from the back side and holds it horizontally, and supports the wafer holder 42 from below, and during the coating process. A rotation mechanism 43 that rotates the wafer holder 42 around the vertical axis is provided.
[0013]
A slit 44 extending in the X direction is formed in the ceiling portion of the case body 41, and a coating nozzle 5 for supplying a coating solution containing, for example, polyimide as a coating film component is formed above the slit 44. The application nozzle 5 is configured to be supported by the nozzle support 52 and moved in the X direction by the drive mechanism 53 in a state where the discharge hole 51 at the side tip protrudes into the case body 41 through the slit 44. For example, the diameter of the discharge hole 51 is about 100 μm, and the coating liquid is discharged onto the surface of the wafer W at a flow rate of 0.05 ml / sec, for example, 10 mm above the wafer W.
[0014]
Further, the nozzle support part 52 has a spray nozzle 54 for spraying the solvent of the coating film on the surface of the wafer W so as to be adjacent to the nozzle 54 on the traveling direction side of the application nozzle 54 via the support part 55, for example. Is provided. The spray nozzle 54 has, for example, a diameter of the spray hole 55 at the tip of the nozzle 54 of about 0.5 mm. For example, the solvent is applied to the surface of the wafer W from the upper side of the wafer W at a flow rate of, for example, 0.025 ml / sec. It is configured to spray.
[0015]
For example, as shown in FIG. 5, the coating nozzle 5 and the spray nozzle 54 spray toward the front side in the traveling direction of the coating nozzle 5 with respect to the discharge position of the coating liquid discharged from the coating nozzle 5 to the surface of the wafer W. The solvent is sprayed from the nozzle 54 onto the surface of the wafer W.
[0016]
Such a coating nozzle 5 is connected to a component tank 63 for storing a component of the coating film such as polyimide, for example, via an opening / closing valve V1, a mixing unit 62, and an opening / closing valve V2 through a flexible component supply path 61. Further, it is connected to a solvent tank 64 for storing a solvent of a coating film such as a thinner solution through an opening / closing valve V3 on the upstream side of the mixing unit 62. The mixing tank 62 is for preparing a coating solution by mixing the components of the coating film and a solvent. However, the coating solution is adjusted in the supply path without installing the mixing tank 62. May be. The spray nozzle 54 is connected to the solvent tank 63 through an open / close valve V4, for example, by a flexible supply path 65. In this example, the amount of the component supplied from the component tank 63 or the solvent tank 64 to the mixing tank 62 or the solvent is controlled by controlling the opening degree of the on-off valves V1 to V4 forming the flow rate adjusting unit by a control unit (not shown). And the flow rate of the coating liquid discharged from the coating liquid nozzle 5 and the flow rate of the solvent sprayed from the spray nozzle 54 are adjusted.
[0017]
Next, the method of the present invention carried out with such a coating film forming apparatus will be described. First, when the cassette C is loaded into the cassette station 21, the wafer W is taken out by the transfer arm 23. Then, the wafer W is transferred from the transfer arm 23 to the main transfer means 25 via the transfer unit 35 in the shelf unit U2, and is transferred into the coating unit 31. The wafer W carried into the coating unit 31 is adsorbed on the back side by the wafer holder 42 and is held substantially horizontally. On the other hand, in the coating liquid supply system, the on-off valve V2 and the on-off valve V3 are opened at a predetermined opening, and a predetermined amount of coating film components and a predetermined amount of solvent are supplied to the mixing unit 62. A coating solution having a predetermined concentration is prepared.
[0018]
Then, while rotating the wafer W at a predetermined number of rotations, the coating nozzle 5 is positioned above the center of the wafer W, and the opening / closing valve V1 is opened to start discharging a predetermined amount of coating liquid. Move gradually in the radial direction toward In this way, the coating liquid is applied on the surface of the wafer W while drawing a spiral pattern.
[0019]
As shown in FIGS. 6 and 7A, for example, 3 mm from the periphery of the coating film formation region of the wafer W from the center of the wafer W toward the peripheral side while discharging a predetermined flow rate of the coating liquid from the coating nozzle 5. The coating liquid is applied to the first region 71 of the coating film forming region of the wafer W by moving the first region 71 to the first position which is an inner position of about 5 mm. Subsequently, as shown in FIG. 6 and FIG. 7B, a predetermined flow rate of the coating liquid is discharged from the coating nozzle 5, and the opening / closing valve V4 is opened to spray the solvent at a predetermined flow rate from the spray nozzle 54. The coating solution nozzle 5 and the spray nozzle 54 are moved to the peripheral position of the coating film forming region, and thus the coating solution is applied to the second region 72 outside the first region.
[0020]
In this way, in the second region 72 on the surface of the wafer W, as shown in FIG. 8, the coating liquid is discharged onto the surface of the wafer W from the coating liquid nozzle 5, and the coating liquid nozzle of the discharged coating liquid is discharged. 5, the coating liquid is applied in a state where the solvent 74 is sprayed from the spray nozzle 54 to the front side in the traveling direction. Thus, in the coating liquid applied to the surface of the wafer W, the first position from the center portion is applied. The second region 72 outside the first region 71 is in a state where the amount of the solvent is larger than that of the first region 71 up to.
[0021]
Next, the wafer W on which the coating liquid has been applied is transferred to the reduced-pressure drying unit 32 which is the first drying means by the main transfer means 25, where the wafer W is heated to, for example, about 50 ° C. For example, as shown in FIG. 7C, the solvent of the coating solution applied to the surface of the wafer W is volatilized and dried. Thereafter, the wafer W is transferred to the heating unit 33 as the second drying means by the main transfer means 25, where it is heated to, for example, about 90.degree. It is conveyed to the cooling unit 34 by the means 25, where it is cooled to, for example, about 23 ° C., thereby forming a coating film made of a predetermined polyimide film 75 as shown in FIG. The wafer W thus cooled is returned to the original cassette C of the cassette stage 22 by the main transfer means 25, for example.
[0022]
According to the above-described embodiment, in the second region on the peripheral side of the coating film forming region of the wafer W, the coating liquid is applied while spraying the solvent on the front side in the traveling direction of the coating solution. Since the amount of solvent is larger than that in the first region, the thickness of the coating film can be made uniform over the entire wafer surface. That is, as described above, the heat dissipation amount in the peripheral region of the wafer W is larger than the other regions, and the volatilization rate of the solvent in the coating film increases in this peripheral region depending on the heat dissipation amount. The amount of solvent volatilization is greater than in other areas.
[0023]
Therefore, if the amount of the solvent in the second region is originally larger than that in the first region and diluted with the solvent, even if the solvent is volatilized more than in the first region, as a result The degree of volatilization of the solvent can be aligned with the first region. In this way, the degree of volatilization of the solvent is almost the same in the wafer W surface, so that the polyimide solidification speed is substantially uniform in the wafer surface. As a result, a polyimide film having substantially the same film thickness is formed over the wafer W surface. Can be formed.
[0024]
Here, the amount of the solvent sprayed from the spray nozzle 54 in the first position or the second region is, for example, changed to various conditions to form a polyimide film on the wafer W and apply the wafer W. It is determined by trial and error by confirming whether or not the peripheral edge of the film forming region is raised. For example, when a polyimide film having a thickness of about 10 μm is formed on an 8-inch wafer W, The first position is preferably a position about 3 mm to 5 mm inside from the peripheral edge of the wafer W, and the amount of the thinner liquid sprayed from the spray nozzle 54 in the second region is In the case where the rotational speed is 15 rpm and the spray nozzle 54 is advanced at a speed of, for example, 1.0 to 1.2 mm / sec, it is preferably about 0.05 to 0.055 ml.
[0025]
Actually, in the coating unit 31 having the configuration shown in FIG. 3, the rotation speed of the wafer W is set to 15 rpm, and the coating nozzle 5 and the spray nozzle 54 are advanced at a speed of, for example, 1.0 to 1.2 mm / sec. Is set to a position 3 mm inside from the peripheral edge of the wafer W, and the amount of the thinner liquid sprayed from the spray nozzle 54 in the second region is 0.05 ml. When a polyimide film having a thickness is formed, the film thickness is measured over the entire surface of the wafer W, and the uniformity of the film thickness is confirmed by a film thickness measuring device (Nanospec M5100), the peripheral region of the coating film forming region No swell of the polyimide film was observed, and it was confirmed that high film thickness uniformity could be secured.
[0026]
In the above example, the coating liquid nozzle 5 and the spray nozzle 54 are applied to the coating film on the wafer W while discharging the coating liquid from the coating liquid nozzle 5 to the second region and spraying the solvent from the spray nozzle 54. The spray nozzle 54 is stopped at the peripheral region of the coating film forming region, and the spray nozzle 54 is stopped at the peripheral region of the coating film forming region. In this state, the solvent is applied onto the coating solution in this region for about 4 to 5 seconds. You may make it spray. At this time, the wafer W remains rotated, and the discharge of the coating liquid from the coating liquid nozzle 5 is stopped. In this way, the solvent can be sufficiently sprayed to the peripheral area of the coating liquid forming area up to the end surface of the coating liquid forming area, and even if the heat dissipation amount of the area is larger than that of the other areas. Since the degree of volatilization of the solvent is aligned with other regions, the uniformity of the film thickness of the polyimide film formed on the wafer W can be improved as a result.
[0027]
In the above-described example, the solvent is sprayed to the front side in the traveling direction of the coating liquid. In this case, the coating liquid is applied to the area where the solvent is sprayed in advance. For this reason, since the contact angle of the coating solution is reduced by the solvent, it is possible to prevent the coating solution from spreading and to prevent the film thickness from expanding. From this point as well, the film in the peripheral region of the coating film forming region can be suppressed. Swelling can be suppressed.
[0028]
Further, in the second region, the number of rotations of the wafer W may be higher by, for example, 5 to 10 rpm than that in the first region, or the moving speed of the coating nozzle may be increased. Furthermore, as shown in FIG. 9, the amount of the solvent sprayed from the spray nozzle 54 may be set to a smaller amount than the example shown in FIG.
[0029]
Further, in the present invention, as shown in the front view of the application nozzle in FIG. 10A and the plan view of the application nozzle in FIG. 10B, the tip position (discharge hole) of the spray nozzle 54 is predetermined around a substantially horizontal axis. You may make it provide so that rotation within the amplitude of this is possible. In this example, for example, the spray nozzle 54 is pivotally supported by the nozzle support portion 52 via the support portion 81, for example, at a substantially central position in the length direction so as to be adjacent to the front side of the coating liquid nozzle 5 in the traveling direction side. For example, the upper side of the spray nozzle 54 is always urged so as to be positioned on the coating liquid nozzle 5 side.
[0030]
Further, inside the nozzle support portion 52, there is provided a pressing portion 82 made of, for example, an air cylinder that presses the upper side from the coating liquid nozzle 5 side with respect to the region supported by the support portion 81 of the spray nozzle 54. By pressing the spray nozzle 54 urged so that the upper side is always positioned on the coating liquid nozzle 5 side by the pressing portion 82, the discharge hole of the spray nozzle 54 rotates with a predetermined amplitude. (Including movement in one direction).
[0031]
In such an example, if the angle of the spray nozzle 54 relative to the coating nozzle 5 is changed by rotating the spray nozzle 54, the traveling direction of the nozzle 5 at the position where the coating liquid is discharged from the coating liquid nozzle 5. In the region in front of the side, the solvent can be sprayed freely in the preferred region. Further, when the spray nozzle 54 is rotated in a state where the solvent is sprayed, the solvent can be sprayed in a wide area with respect to a region in front of the application nozzle 5 on the traveling direction side. In this way, spraying the solvent from the spray nozzle 54 in various forms is effective because the solvent can be sprayed according to the recipe of the coating process.
[0032]
As described above, according to the present invention, in the second region of the coating film forming region of the wafer W, the coating nozzle 5 is positioned forward of the coating nozzle 5 on the front side in the direction of travel of the coating solution from the position where the coating solution is discharged onto the wafer surface. Although spraying the solvent is desirable from the viewpoint of spraying the thinner directly on the volatile surface, the solvent may be sprayed at substantially the same position as the position where the coating liquid is discharged from the coating liquid nozzle 5 onto the wafer surface. Alternatively, the solvent may be sprayed on the rear side of the application nozzle 5 in the traveling direction of the application liquid discharge position.
The spray nozzle 54 is provided separately from the coating nozzle 5, and the coating liquid nozzle 5 and the spray nozzle 54 are moved separately in the second region to discharge the coating liquid onto the wafer surface and spray the solvent. May be performed. Further, in the second region, the solvent may be sprayed to the peripheral region without moving the spray nozzle 54 while being positioned on the peripheral side of the coating film forming region, and this region may be used as a solvent atmosphere. As shown in FIG. 5, the spray nozzle 54 that can rotate about a substantially horizontal axis is used to spray the solvent in a wide range while rotating the spray nozzle 54 without changing the position of the spray nozzle 54. Good.
[0033]
Further, in the present invention, the spray nozzle 54 is not provided, and the supply system of the coating nozzle 5 is provided between when the coating liquid is discharged to the first area and when the coating liquid is discharged to the second area. When the opening of the opening / closing valve V3 is adjusted by the control unit and the second region is applied, the opening of the opening / closing valve V3 is controlled so as to increase the solvent from the solvent tank 64 to the mixing unit 62. The supply amount may be increased, thereby increasing the solvent amount in the second region. Moreover, you may make it use a mass flow controller as a flow volume adjustment part. Furthermore, although this invention described the Example about the coating film which uses a polyimide film as a component, it can apply also to application | coating of a coating liquid with high viscosity, for example, a resist liquid.
[0034]
【The invention's effect】
As described above, according to the present invention, when forming a coating film by spirally discharging a coating solution onto a substrate, coating with a highly uniform film thickness is suppressed by suppressing the swelling of the film in the peripheral region of the coating film forming region. A film can be formed.
[Brief description of the drawings]
FIG. 1 is a plan view showing the overall structure of a coating film forming apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view showing an overall structure in the embodiment.
FIG. 3 is a longitudinal sectional view for explaining a coating unit used in the embodiment.
FIG. 4 is a plan view for explaining the coating unit.
FIG. 5 is a side view for explaining an application nozzle and a spray nozzle used in the application unit.
FIG. 6 is a characteristic diagram for explaining the operation of the present embodiment.
FIG. 7 is a process diagram for explaining the operation of the present embodiment.
FIG. 8 is a side view for explaining the operation of the application nozzle and the spray nozzle.
FIG. 9 is a side view for explaining the operation of the application nozzle and the spray nozzle.
FIGS. 10A and 10B are a front view and a plan view showing another example of an application nozzle and a spray nozzle. FIGS.
FIG. 11 is a plan view for explaining a conventional coating film forming method.
FIG. 12 is a cross-sectional view for explaining a conventional coating film forming method.
[Explanation of symbols]
C cassette W wafer S1 processing unit U1, U2, U3 shelf unit V1, V2, V3 open / close valve 21 cassette station 25 main transfer means 31 coating unit 42 wafer holding unit 43 rotating mechanism 5 coating nozzle 53 drive mechanism 54 spray nozzle 61 component supply Path 63 component tank 64 solvent tank 65 solvent supply path

Claims (4)

While rotating the substrate holding portion that holds the substrate substantially horizontally about the vertical axis, while discharging the coating liquid containing the component of the coating film and the solvent from the coating nozzle provided facing the surface of the substrate, In the coating film forming method in which the coating nozzle is moved from the center of the substrate toward the peripheral side, whereby the coating liquid is spirally applied to the surface of the substrate .
A step of applying the first region of the coating film forming region by moving the coating nozzle from the center of the substrate toward the first position while discharging the coating liquid to the first position ;
Next, the coating nozzle is moved toward the peripheral side of the substrate while discharging the coating liquid, and is applied to the second region which is the peripheral region of the substrate outside the first region. Spraying the solvent of the coating film onto the second region from a spray nozzle that moves toward the peripheral side . The coating liquid is applied to the second region by the coating nozzle and the spray nozzle, respectively, and after spraying the solvent, the second spray nozzle is discharged from the spray nozzle in a state where the discharge of the coating liquid from the coating nozzle is stopped while the substrate is rotated. The coating film forming method according to claim 1, wherein the step of spraying the solvent onto the coating solution at the peripheral position of the region is performed . A substrate holder for holding the substrate substantially horizontally;
A rotation mechanism for rotating the substrate holding portion around a substantially vertical axis;
Provided surface facing the substrate, and the coating nozzle for discharging a coating solution containing a component and a solvent for the coating film to the substrate surface,
And the spray nozzle for spraying the solvent of the coating film,
A moving mechanism for moving the coating nozzle and the spray nozzle in a substantially horizontal direction in the radial direction of the substrate ,
The substrate holding portion is rotated and the coating nozzle is moved from the center of the substrate toward the first position while discharging the coating liquid to the first position, so that the first region of the coating film forming region is spirally coated. Next, the coating nozzle is moved toward the peripheral side of the substrate while discharging the coating liquid, and is applied spirally to the second region, which is the peripheral region of the substrate outside the first region. A coating film forming apparatus that sprays the solvent from the spray nozzle onto the second region while moving the spray nozzle toward the outside of the substrate together with the nozzle . 4. The coating film forming apparatus according to claim 3, wherein the spray nozzle is configured to be rotatable with a predetermined amplitude around a substantially horizontal axis.

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